The development of solid block cleaning compositions has revolutionized the manner in which detergent compositions are dispensed by commercial and institutional entities that routinely use large quantities of cleaning materials. Solid block compositions offer unique advantages over the conventional liquids, granules or pellet forms of detergents, including improved handling, enhanced safety, elimination of component segregation during transportation and storage, and increased concentrations of active components within the composition. Because of these benefits, solid block cleaning compositions, such as those disclosed in U.S. Pat. No. RE 32,763, U.S. Pat. No. RE 32,818, U.S. Pat. Nos. 4,680,134 and 4,595,520, have quickly replaced the conventional composition forms in commercial and institutional markets.
Various attempts have been made to develop a process for converting a liquid cleaning composition to a solid mass for containment and dispensing of the active ingredients during use. For example, the ingredients of the cleaning composition have been combined and subjected to melting temperatures to achieve a homogeneous mixture in that is commonly referred to as a "molten process," and then poured into a mold and cooled to a solid form.
Solid alkaline detergent compositions have also been prepared from an aqueous emulsion of detergent ingredients and substances that will hydrate to bind free water in the emulsion which, optionally after heating and cooling, hardens to a solid. For example, U.S. Pat. Nos. 4,595,520 and 4,680,134 to Heile et al., disclose a solid alkaline detergent formed from an aqueous emulsion containing a sodium condensed phosphate hardness sequestering agent and an alkaline builder salt such as sodium hydroxide, which is solidified by incorporating a hydratable hardening agent such as an anhydrous sodium carbonate and/or sodium sulfate. Preferably, the emulsion is heated to form a molten mass, and then cooled to effect solidification. U.S. Pat. No. 5,064,554 to Jacobs et al., discloses a solid detergent in the form of a fused block that is manufactured by preparing a melt of alkali metal silicate, alkali metal hydroxide, optionally water, an active chlorine donor and/or an organic complexing agent, combining the melt with a penta-alkali metal triphosphate, introducing the melt into a flow mixer, and pouring the molten mixture into a mold to solidify. U.S. Reissue Pat. No. RE 32,763 to Fernholz et al., discloses a method of manufacturing a solid block cleaning composition by forming an aqueous solution of two hydratable chemicals, such as sodium hydroxide and sodium tripolyphosphate, heating the solution to a temperature of about 65-85.degree. C., increasing the concentration of the hydratable ingredients in the heated solution to provide a composition which is liquid at an elevated temperature and solidifies at about room temperature, and casting the heated solution into molds whereupon the composition solidifies upon cooling.
Solid block cleaning and sanitizing compositions and rinse aids provide a significant improvement over the conventional liquid, granular and pelletized cleaning compositions. Although the molten process is useful for preparing solid block compositions, time and expense would be saved if heating and cooling of the composition could be eliminated from the process. Also, lower process temperatures would better facilitate the use of heat-sensitive ingredients in cleaning compositions. In addition, less sturdy packaging would be required if the processed mixture could be dispensed at a lower temperature.
Attempts have been made to develop processes that decrease the amount of contact of thermally-sensitive ingredients with molten ingredients in order to minimize the deactivation of such ingredients. For example, U.S. Pat. No. 4,725,376 to Copeland, et. al., discloses manufacturing a solid block, alkaline cleaning composition by placing solid particles of the thermally-deactivatable ingredient into a mold, pouring the molten alkaline ingredient over the solid particles so it percolates into the interstitial spaces, and then cooling the melt to a solid form. The resulting solid block cleaning composition comprises granules of the thermally-deactivatable ingredient uniformly dispersed throughout the composition.
Other attempts have been made to improve and simplify the molten process by blending the ingredients without melt temperatures. For example, U.S. Pat. No. 4,753,755 to Gansser, discloses combining a hardness sequestering agent and an aqueous alkaline solution at a temperature of between 50-130.degree. F. to form an alkaline liquid dispersion, and then adding a solidifying amount of a solid caustic material to the dispersion. U.S. Pat. No. 2,164,092 to Smith, discloses solidifying an aqueous alkaline solution by adding a metaphosphate compound under conditions which will convert the metaphosphate to an orthophosphate and/or pyrophosphate and hydrate the water to solidify the alkaline solution. While the processes of Gansser and Smith provide a method for the manufacturing solid block cleaning compositions without melt temperatures, the process of Gannser generally produces compositions that require extended mixing times and several hours to solidify, is limited to nitrilotriacetic acid compositions, may require hours to build viscosity to a level of substantially no flow, and requires three long mix times to prevent product separation, and Smith's process is limited to phosphate-based cleaning compositions.
Various attempts have also been made to manufacture cleaning compositions by an extrusion process. U.S. Pat. No. 5,061,392 to Bruegge et al., for example, discloses a method of forming a detergent composition having a paste-like consistency, by combining a first aqueous solution containing a potassium tripolyphosphate and a second aqueous solution containing a water-soluble, sodium-based detergent builder, namely sodium hydroxide. Upon mixing, the viscosity of the mixture rapidly increases to form a highly viscous paste. In another extrusion method, as disclosed in U.S. Pat. No. 4,933,100 to Ramachandran, an organic detergent of particulate or patty form is formed by kneading together a synthetic organic detergent, a hydratable builder salt such as sodium tripolyphosphate, and water. The mixture is passed through an extruder and forced through openings at or slightly above room temperature and a low pressure to form a rod-shaped extrudate. A disadvantage of these processes is that neither method provides a final product that is a fused solid block upon hardening.
Therefore, an object of the invention is to provide a process for manufacturing a solid, highly alkaline cleaning composition at a process temperature at or below the melt temperature of the ingredients. Another object is to provide a process for making a highly alkaline cleaning composition at a low processing temperature and high viscosity to achieve rapid solidification of the cast or extruded composition. A further object is to provide a process that will substantially eliminate swelling of the solid cast or extruded composition and product.